1. Field of the Invention
This invention relates to a heating roller device for a laminator that is used to fix a plastic protective film onto a sheet, such as a photograph, and more particularly to a heating roller device, which includes a heating element that is disposed in a roller for heating the roller by radiation.
2. Description of the Related Art
Referring to FIG. 1, a first conventional laminator is shown to include a heating roller device that consists of two heating rollers 7, and two heating elements 8 for heating the rollers 7, respectively. The rollers 7 are driven by a driving unit (not shown) to rotate in opposite directions. A plastic protective film 91 and a sheet 9, which are superposed, are fed into a space between the rollers 7. As such, the film 91 and the sheet 9 can move between the rollers 7, thereby fixing the film 91 to the sheet 9 under heat and pressure. However, air voids are formed between the film 91 and the sheet 9 during the heat pressing process. Referring to FIG. 2, a second conventional laminator solves this problem, and is shown to include a pair of front rollers 71, a pair of rear rollers 72, and a pair of heating elements 8xe2x80x2 that are disposed between the front and rear rollers 71, 72. The assembly of the film 91 and the sheet 9 is fed into a space between the front rollers 71 so as to discharge air from a space between the film 91 and the sheet 9. Thereafter, the assembly is moved and heated between the heating elements 8xe2x80x2, and is subsequently fed into a space between the rear rollers 72, thereby interconnecting the film 9 and the sheet 91 fixedly under pressure.
Referring to FIGS. 1 and 2, because the heating elements 8, 8xe2x80x2 are disposed outside the rollers 7, 71, 72, the heating efficiency is relatively poor. Moreover, the heating elements 8, 8xe2x80x2 occupy much space in the conventional laminators.
The object of this invention is to provide a heating roller device for a laminator, which includes a heating element that is disposed in a roller, thereby increasing the heating efficiency and reducing the volume of the laminator.
According to this invention, a heating roller device is used to fix a film to a sheet in a laminator, and has two heating rollers. Each of the rollers includes a hollow support shaft, a roller body disposed rotatably around the support shaft, and a heating element disposed in the roller body. An electrical wire extends into the support shaft, and is in electrical connection with the heating element.
Preferably, the roller body is coated with a soft wear-resistant material, such as TEFLON, that is in tight engagement with the assembly of the film and the sheet so as to prevent formation of air voids between the film and the sheet.